Bubble cap



W. W. KRAFT June 6, 1950 BUBBLE CAP v F1186 D96. 18. 1947 IN VEN TOR. WW

Patented June 6, 1950 2,510,589 BUB LE CAP Wheaten W. Kraft, Scarsdale, N. Y., assignor to The Lummus Company, New York, N. Y., a corporation of Delaware Application December 18, 1947, Serial No. 792,389

6 Claims. (Cl. 261-114) This invention relates to bubble caps and to methods of making the same, and is particularly directed toward improvements in the means for breaking up the gas or vapor into bubbles before they rise through the liquid, immersing the lower edge of the cap skirt, whereby their size and spacing may to a large degree be predetermined.

It is a general object of the present invention to provide a novel and improved bubble cap whereby to predetermine and control the size and spacing of bubbles emitted from beneath the lower edge of the same when in use.

More particularly it is an object of the invention to provide a skirted bubble cap with simplified fringe or comb means for breaking up the gas into bubbles of predetermined size and spacing, which means is extremely simple to manufacture and apply to the cap.

An important object of the invention consists in the arrangement of a bubble cap and separately formed comb structure and the manner of applying it to the skirt of the cap to predetermine the bubble size and spacing.

A further important object of the invention consists in the formation of the comb from a series of depending rods or wire lengths which may comprise elements of a bent sinuous rod or wire.

A still further important feature of the invention consists in forming a comb element for use with the straight edged skirt of a bubble cap comprising a continuous length of rod or wire bent into alternate bights and uniform stretchers for application about the periphery of and extending below the edge of a skirt with the upper bights welded to the skirt.

One of the exclusive features of the comb construction just defined is its capability of being stretched or compressed longitudinally whereby to automatically regulate the spacing between the stretchers which determine the number of bubbles about the periphery of the skirt.

Other and further features and objects of the present invention will be more apparent to those skilled in the art upon a consideration of the accompanying drawing and following specification, wherein are disclosed several exemplary embodiments of the invention, with the understanding that such modifications and combinations may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.

In said drawings:

Fig. 1 is a central vertical section through a bubble cap assembly constructed in accordance with the present invention and taken on line 1-4 of Fig. 2;

modification in which the cap is supported by the teeth of the comb;

Fig, 4 illustrates in side elevation a further embodiment showing a punched comb unit directly applied to the cap; and

Fig. 5 is a horizontal cross-section on line 5-5 of Fig. 1 showing a detail of the depending teeth.

Bubble caps arranged in cooperation with risers extending from openings in the deck-plates of towers or columns, used in the chemical and refining industries for many purposes, bring bubbles of a gas or vapor into intimate contact with a liquid being treated. The great demand and widespread varied use has resulted in many types of such caps, varying from complex cast and/or machined units to those relatively simple ones stamped or pressed from sheet metal into the desired shape, usually that of an inverted pot or bowl. Early forms of bubble caps usually had a simple, unperforated depending skirt with a straight lower ,edge immersed below the level of the liquid on the deck and beneath which the gas or vapor, coming through the riser perforating the plate, bubbled and rose to the surface, thus remaining in contact with the liquid for the depth of immersion of the skirt. It was soon recognized that such caps did not offer proper control of bubble size and spacing and many attempts were made to provide a perforated skirt or toothed or sinuous form to the skirt edge to break up the bubbles into small size for more intimate contact with the liquid. Such caps presented additional problems in manufacture. The cast caps, being unmachined, could not be made accurately enough to insure a uniform depth to the spaces between teeth to insure that they would all be used in discharging vapor. Caps with machined teeth were expensive and difficult to manufacture. Punching was not satisfactory in the case of stamped or drawn caps because of the difliculty of controlling the apertures or teeth if they were out before the drawing operation and the almost impossible problem of cutting them during or after forming except on expensive indexing shapers.

Bubble caps of substantially uniform size and shape may be used for many processes but depending on the liquid and the gas or vapor, the spacing and/or width of the teeth become important in controlling the operation to produce the desired number and size of bubbles.

In accordance with the present invention it is proposed to make the cap and skirt as an integral structure by any of the operations heretofore used,

3 but the lower edge of the skirt is formed or cut of! straight and horizontal so that it will be immersed in the liquid to a uniform depth all around and similarly spaced from the surface of the deck. A comb having the proper width and spacing of teeth to provide the bubblesizing and spacing is then applied to the skirt. Preferably the rods are relatively straight stretchers or lengths in a sinuous wire bent to have short radii bights connecting alternate ends of the stretchers. Such a comb unit may be preconstructed of the desired wire diameter and bent other and can be adjusted before or during the application to the skirt of the cap to decrease or increase the circumferential spacing between the stretchers by compressing or stretching the now band-like unit or sinuous wire. This permits variations in the number and spacing of the comb teeth without any substantial changes in the construction methods and assembly of the several parts. This provides an extremely simple and cheap construction which in operation is equally as effective as the bubble caps produced by the more costly and slower processes referred to above. Since the bottom edge of the cap and not the notches between the comb teeth is the controlling factor in immersion depth much greater accuracy is assured at no increased cost.

Referring now to the drawings for a better understanding of the invention, and first to Figs. 1 and 2, there is shown at III a substantially horizontal plate or deck forming a portion of a treating tower assembly of more or less conventional type, such as shown, for instance in the patent to Risdon, No. 1,711,656. In a manner such as shown in that patent, means is provided for causing a liquid to flow across the plate at a level approximately as indicated by Line L. The deck is perforated in a number of places as at I] and each of the perforations receives a vertical tubular riser l2. Such riser, formed circular in crosssection or in any other desired configuration,

. may be attached in a liquid-tight manner to the plate in any of a number of well known ways. Conveniently the riser or sleeve fits closely in the perforation 'in the plate and is welded thereto about its periphery at the level of the upper surface of the plate, as shown at l3. The upper end ll of the riser is preferably cut off horizontally. The bubble cap unit I 5 is shown as of the pressed metal type, although it will be understood that other types are equally as adaptable to this invention. It comprises a substantially fiat top It and a vertically depending cylindrical skirt i1 conventionally merged with the top along a large radius I. The lower edge of the skirt is straight, continuous and horizontal when the cap is) mounted above a riser l2 and concentric there- In Figs. 1 and 2 such mounting is effected by securing, as by welding or the like, a plurality, preferably three brackets 22 to the inner surface of a cap near the junction of the skirt and top, which perform the combined functions of co-axially spacing the riser and cap, separating the cap top from the mouth of the riser and the skirt edge 20 from the deck. For this purpose each bracket is notched as at 23 by the junction of vertical and horizontal surfaces appropriately spaced and positioned to respectively and closely engage both the outer walls of and the top edges of the riser. Thus the cap is accurately positioned by merely setting it down over the riser. Any appropriate form of hold-down, such as those heretofore known in the art may oe used if necessary to insure against the cap lifting of! of the riser under the action of the ascending gases or vapors.

To insure uniform breaking up of the gas or vapor emerging from the riser and being forced to pass beneath the surface of the liquid by the submerged edge of the skirt, a suitable comb assembly 25 is applied about the periphery of the skirt and attached thereto with the major portion of the comb teeth depending beneath the skirt edge.

This then does not require careful machining of the comb since the edge beneath which the bubbles pass is the lower edge of the cap and not the bottoms of the notches between the teeth. By merely making this lower edge smooth, straight and horizontal, uniform bubbling is effected. In the structure shown in Figs. land 2 the comb is very simply made by bending a wire or rod, preferably of circular cross-section, into a sinuous form composed of alternate relative ly straight stretchers or lengths 21 and connecting bights 28 and 29, preferably of about 180 arcuate extent.

Such bent up wire is wrapped as a strip about the periphery of the skirt with substantially only the upper bights 28 resting thereon and these are welded or otherwise secured thereto in a substantial manner. This provides for uniform spacing between the stretchers, lengths or teeth and again makes use of the lower edge of the skirt, which lies in a plane perpendicular to the axis of the cap, for determining the actual depth of liquid through which the gas is bubbled; The wire may be of any desired diameter and the radius of each bight may be predetermined, but it is simpler to make use of sinuous wires of the same manufactured pitch or spacing between the teeth and to then change this spacing as desired, in accordance with the use to which the caps are to be put, by merely stretching out or compressing the resultant formation, thus changing the tooth spacing in accordance with any predetermined calculations.

In Fig. 3 the structure does not differ substantially from that shown in Fig. l, for the cap element is identical. The brackets 32, however, can be simplified since they are not requiredto support the cap. Hence they have only the straight vertical inner edges 33 adapted to abut the vertical sides of the riser tube l2. The cap is supported by permitting the lower bights 29 of the comb structure to rest on the surface of the deck III. For this purpose the teeth are shown as of greater length than in Fig. '1, whereby the lower edge 20 of the cap skirt is supported at about the same distance above the level of the deck; This form of the invention partakes of all of the benefits of the first form described.

In Fig. 4 a further embodiment is illustrated. Such a comb assembly or toothed structure may be formed from suitable sheet metal, as for instance, by punching or cutting from a solid strip which may then be wrapped around and welded to the skirt with such a positioning that the full length of tooth does not depend from the skirt edge. In this case the supporting means for the cap is not illustrated but may be of any well known form. The skirt [1, however, has the same horizontal lower edge 20. Secured about its periphery is a bubble spacing and sizing means punched from a piece of sheet metal and including a base band 4| and a series of straight elements of rod or wire 38 with spacing 39 shown in accordance with predetermined computations. The short overlap 40 of each of these elements with the skirt provides adequate space for welding and insures as in previous cases that the lower edge of the cap determines the total bubble depth. Obviously the rods may be long enough to rest on the deck or may be cut off to the short length indicated. Their cross sectional area, shape and spacing are subject to change in accordance with use predetermined for the cap. Their method of assembly may comprise the initial mounting thereof in suitable bendable spacing means to hold them during the welding operation.

In each of the structures an extremely simple means is provided for obtaining the desired bubble sizes and spacing while reducing the necessary work in providing the cap. Obviously where serious corrosion, erosion or chemical action results tending to shorten the life of the relatively thin teeth they may be constructed of more expensive highly resistant material than is the heavier cap, adding a further note of economy in the whole structure.

As shown in Fig. which is a cross section through two of the rods or teeth 21 of Fig. 1, the

opening closely approximates a venturi. As a result, the pressure drop of vapors which pass through the space 30 is considerably lower than for sharp edged openings customary in prior practice. While the advantage of this Venturi efiect differs with diameter of rods or teeth and spacing, it is possible to obtain a coeflicient of discharge as much as twice that of the sharp edged opening and it is thus possible to reduce the pressure drop or increase the throughput. Inasmuch as pressure drop has a substantial effect at the temperature used in vacuum distillation, it is possible under certain circumstances to recover additional high boiling materials without exceeding the maximum allowable temperatures as regards decomposition.

The term rod or rod-like is used herein to denote lengths, elements or teeth of metalof such cross-section and stiffness as is requisite for providing with the cap the bubble openings.

It is of course, to be understood that the Venturi effect between the teeth may also be accomplished if the teeth are in the form of truncated cones, as for example, teeth that are cast on the edges of the caps. An oval shape may also be m I I anal While I have shown preferred forms of embodiment of my invention, I am aware that other modifications may be made thereunto which come within the scope and spirit of the description herein and of the claims appended hereinafter.

I claim:

1 A bubble cap unit comprising a metal bubble cap with a depending peripheral skirt having innot and outer surfaces and a lower edge, said lower edge lying in a plane perpendicular to the axis of said cap, and it separately formed bubble spacing and sizing means comprising a continu- 3. The bubble cap unit of claim 1 in which the I comb-like strip comprises a sheet metal band having the rod-like elements extending integrally from one side edge thereof.

4. A bubble cap unit comprising a pressed metal bubble cap with a depending peripheral skirt having inner and outer surfaces and a lower edge, said lower edge lying in a plane perpendicuiar to the axis of said cap, and a sheet metal band formed with spaced teeth extending from one side edge thereof, said metal band being secured to one of said skirt surfaces adjacent the lower edge portion and coextensive therewith, and said teeth extending from a point above to a point below, said skirt edge.

5. A bubble cap assembly comprising a plate with a riser extending therethrough, a metal bubble cap with a depending peripheral skirt having inner and outer surfaces and a straight lower edge mounted over said riser in spaced relation to the plate, the lower edge of said skirt lying in a plane extending parallel to the plate, and a sinuously shaped strip of wire integrally secured to one of said skirt surfaces adjacent the lower edge portion and coextensive therewith, said strip having uniformly spaced straight lengths extending from a point above to a point below, said skirtedge for determining bubble spacing and sizing.

6. The combination of claim 5 in which extending portions ofsaid strip of'wire engage the plate in cap supporting relation.

WHEATON W. KRAFT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 7 Name Date 314,498 Van Gelder Mar. 24, 1885 1,286,951 Davies Dec. 10, 1918 1,482,408 Piron Feb. 5, 1924 2,060,601 Wentworth Nov. 10, 1936 2,070,067 Rice Feb. 9, 1937 2,084,726 Duey June 22, 1937 2,206,284 Eckart June 18, 1940 FOREIGN PATENTS Number Country Date 755,019 France Sept. 4, 1933 885,548 France May 81, 1943 

